The objectives of this proposal are to develop automated, feedback controlled, drug administration devices which function to continuously monitor a drug's effect(s), process the data in real time, and control a servopump which meters out the drug in response to the subject's momentary needs. Two rapid-acting hypotensive drugs will be studied: trimethaphan camsylate (arfonad), and sodium nitroprusside (nipride), both of which have been proven feasible in this application. Also, this technique is being applied to the administration of an anesthetic agent, thiopental, and may be extended to antiarrhythmic drugs, skeletal muscle relaxants, and coronary vasodilators. Experiments with normal and hypertensive dogs will be designed to establish the best type of control schemes and controller settings which rapidly lower blood pressure and maintain it at a desired level. Results will be interpreted with regard to supplying the technique and hardware for subsequent human testing. Hardware includes a portable controller to be interfaced with a blood pressure transducer and a servopump which administers the drug intravenously. The devices will be designed for use in the treatment of hypertensive emergencies and to accomplish controlled reduction of blood pressure over prolonged periods of time as may be desirable during surgery and in certain treatments of hypertension.